I think he just used a compass that has the points on either end as a guided hole punch. By setting it to a certain width he could be sure the spacing was the same between every hole. Then he used the divots left to line up the drill bit. At least that's what I would do.

Loved the detail on your video, V gouge and 6 0z leather and the plastic wrap! (loved that little trick!)... they say the devil is in the details.

I got most of it, just what sort of stitching do you use? I have some tougher "BlueJean" Thread I would like to use, but I've not done this before. Also, how do you get the Pen marks out of the leather?